Noiseless sound reproducing system



AWELE 9 J. HAMMOND, JR 2,@38,99

noxsmmzss SOUND REPRODUCING SYSTEM Filed Aug. 15, 1953 a Sheets-Sheet 1 IN VENTOR JOHN HAYS HAMMOND, JR.

A TTORNEYS mags Amifi 28,1936.

J. H. HAMMOND, JR

NOISELESS SOUND REPRODUCING SYSTEM Filed Aug. 15, 1935 3 Sheets-Sheet 2 [NVENTOR A ril 28, 1936. w JJH. HAMMOND, JR

NOISELESS SOUND REPRODUCING SYSTEM Filed Aug. 15, 1935 5 Sheets-Sheet 3 INVENTOR J D' MM m w W A A H M A H N H Y O Patented Apr. 28, 1936 UNITED STATES PATENT OFFICE 18 Claims.

This invention relates to sound reproducing systems and more particularly to a means for suppressing the scratch and ground noise when no selection is being reproduced.

The invention provides means for stopping the reproduction of the sound record whenever silence is recorded on the record.

The invention further provides means in connection with an amplifier for sound records whereby said amplifier is rendered inoperative whenever there is no selection recorded on said sound record.

According to a preferred embodiment of the invention a photographic film is provided with a sound track which is printed in two or more colors. The sound track, where a selection is recorded, is printed in one color and the sound track, where no selection is recorded, is printed in another color. Suitable pick-up devices such as photoelectric cells with color filters may be provided for picking up the different colored portions of the sound track. One of these pickup devices may control the energy supplied to the sound rep-roducing apparatus, while the other may control means for making said sound reproducing apparatus inoperative when no selection is being reproduced.

The invention also consists in certain new and original features of construction and combinations of parts hereinafter set forth and claimed.

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, the mode of its operation and the manner of its organization maybe better understood by referring to the following description taken in connection with the accompanying drawings forming a part thereof, in which Fig. 1 illustrates a photographic film of the variable area type having a sound track produced in two colors.

Fig. 2 illustrates a photographic film of the variable density type having a sound track produced in two colors.

Fig. 3 is a diagrammatic view partly in section of a moving picture projector and. accompanying circuits constructed in accordance with this invention.

Fig. 4 illustrates diagrammatically a modified form of circuit used in connection with the projector shown in Fig. 3.

Like reference characters denote like parts in the several figures of the drawings.

In the following description and in the claims,

parts will be identified by specific names for convenience, but they are intended to be as generic in their application to similar parts as the art will permit.

Formaking the sound record shown in Fig. 1 5 any sort of variable area recording means may be employed. By this means the area II on the film I2 will be exposed to light producing a transparent area when the film is developed and printed. The area l4 to the left of the line [3 shows the re- 10 cording of .a selection. The area l5 to the right of this line shows no sound recorded. In making up the film'the area I4 is printed in one color, such for example as green, and the area 15 is printed in another color such as purple. This coloring 15 may be done by any suitable method and the location of the line l3 may be determined in any desired manner, such for example as a mark made on the film when the picture is being taken at the time when no sound is being recorded, or it may be determined by a microscopic examination of the film after it .has been developed. In any case a film will be produced which is printed in one color where a selection is recorded and is printed in another color where silence is recorded. 5

Fig. '2' shows a variable density film IS in which the area to the left of a line I! shows the recording of a selection and the area to the right of this line shows the recording of silence. These two areas are printed in different colors in a man- 30 ner similar to that described in connection with Fig. 1.

Referring to Fig. 3 the film I2 is shown placed in a projecting apparatus 2| which is provided with the usual rollers 22 which feed the film. 35 Mounted in front of the film I2 is a casing 23 which contains two lamps 24 and 25. The light from these lamps is focused by means of two lenses 26 and 21 upon a narrow slit 28. Behind the film I2 is a second casing 3| in which are 40 mounted two lenses 32 and 33. These lenses focus the light which passes through the film l2 through two color filters 34 and 35 upon two photoelectric cells 36 and 31. The color filter 34 permits only the light which passes through the green part M of the film l2 to be focused upon the photoelectric cell 36 and the color filter 35 permits only the light which passes through the purple part I5 of the film l2 to be focused upon the photoelectric cell 3-1.

The photoelectric cell 36 is connected through a transformer 4| to the input of a space discharge device 42. The output circuit of this device is connected through a second transformer 43 to an amplifier 44 of any suitable construction, the 55 output of which is connected to a loud speaker 45. The photoelectric cell 3'! is connected to a sensitive relay 46 the contact of which is connected to the blade 41 of a single pole double-throw switch. One contact 48 of this switch is connected to the grid of the device 42 and the other contact 49 is connected to one side of a battery 5| the other side of which is connected to the filament of the device 42. The armature of the relay 46 is connected to the grid return of the device 42 which includes a potentiometer 52 for adjusting the bias.

In the operation of the form of the invention shown in Fig. 3 the film l2 isfed between the walls of the casings 23 and 3| by means of the rollers 22 in the usual manner.- As the sound track passes behind the slit 28 light from the lamps 24 and 25 will be focused on this record by means of the lenses 26 and 21. As long as a selection is recorded on the film in green, only green light will pass through thelenses 32 and 33 to the filters 34 and 35. The filter 34 will allow this light to'pass through and be focused on the photoelectric cell 36 while the filter 35 will prevent the passage of this light, so that the photoelectric cell 31 will not be illuminated.

The pulsating current from the photoelectric cell 36 will pass through the transformer 4| to the input circuit of the device 42 where it will be amplified and fed through the transformer 43 to the amplifier 44, where any desired amount of amplification may be produced and the output fed to the loud speaker 45 where the selection is reproduced as speech or music in the usual manner.

When that portion of the sound track printed in purple, on which silence is recorded, comes opposite the slit 28 only purple light will pass through the lenses 32 and 33 to the filters 34 and 85. The .filter 34 will prevent the passage of this light so that the photoelectric cell 36 will not receive any illumination. The filter 35 however will permit the passage of the purple light, thus illuminating the photoelectric cell 31 which will cause the energization of the relay 46.

. If the blade 41 is thrown in the up position the input circuit of the device 42 will be short circuited when the relay 46 is closed, thus preventing the operation of. the device 42 and therefore preventing any sound whatsoever being produced by the loud speaker 45. If the blade 41 is in the down position the negative potential determined by the voltage of the battery 5| will be applied to the grid of the device 42, thus producing such a high bias on this device that it will prevent its operation so that no sound can be produced by the loud speaker 45.

It is thus seen that when silence is recorded on the film the device 42 will be made inoperative, so that no sound can be produced by the loud speaker 45, in this way eliminating any possibility of ground noises and scratch being produced which might otherwise be heard during periods when silence has been recorded on the film. In this way any scratches or other defects on the film will not produce undesirable noises as they are apt to do under the present systems of sound recording.

Referring to the modified form of the invention shown in Fig. 4 the same type of projecting apparatus 2| is used as shown in connection with Fig. 3. In this figure, however, only the two photoelectric cells 36 and 31 are shown. The photoelectric cell 36 in this case is connected through a transformer 6|, an attenuator 62 and I with a battery 15 and a resistance 76.

a second transformer 63 to the input circuit of three stages of push-pull amplification 64, 65, and 66. The output circuit of the last stage 66 includes the primary of the transformer 43 which, as shown in Fig. 3, is connected to the amplifier 44 and loud speaker 45. Filament current for the space discharge device of the amplifier is supplied through a transformer 6'! from a source of A. C. supply 68. Plate potential for these devices is supplied from a battery 69 which is connected across a resistance H shunted by a condenser 12. The cathode potentials of the three stages of amplification are determined by taps on the resistance H.

i The photoelectric cell 31 is connected in series This resistance is in the input circuit of a space discharge device 77. The plate circuit of this device includes the secondary of a transformer 18, the primary of which is supplied with A. C. from a source 19. 'Filament current for the device 11 is supplied from a second secondary of the transformer 18. The'cathode of the device 11 is connected through a battery 8| to ground and through a resistance 82 to the grid returns of the three stages of push-pull amplification 64, 65, and 66. V

In the operation of the form of the invention shown in Fig. 4 when the sound record which has a selection recorded thereon passes in front of the slit 28 (see Fig. 3) only green light will pass through, which will affect the photoelectric cell 36 but will not affect the photoelectric cell 31, as described in connection with Fig. 3. Pulsating current from the photoelectric cell 36 will pass through the transformer 6|, attenuator 62 and transformer 63 to the three stages of push-pull amplification where the current will be amplified and pass through the transformer 43, amplifier 44 to the loud speaker 45 (see Fig. 3), where it will be reproduced as speech or music in the usual manner.

When the area l5 of sound record l2 having only silence recorded thereon passes in front of the slit 28 only purple light will pass through, which light will afiect the photoelectric cell 31 and not the photoelectric cell 36. This will allow current to flow from the battery 15 through the resistance 76 in the direction of the arrow, thus causing a potential diiference to be produced across this resistance which will cause a large positive potential to be applied to the grid of the device 11, thus decreasing its impedance and allowing more current to flow through this device and through the resistance 82 in the direction of the arrow. This will cause a potential difference to be built up across this resistance, thus causing a high negative potential to be applied to the grids of the space discharge devices in the push-pull amplifiers. This will increase the impedance of these devices to such an amount that they will no longer function as amplifiers, thus making the system inoperative, so that no sound can be produced by the loud speaker 45. In this way any scratch or ground noise which might be present in the film will be entirely suppressed.

Although only a few of the various forms in which this invention may be embodied have been shown herein, it is to be understood that the invention is not limited to any specific construction, but might be embodied in various forms without departing from the spirit of the invention or the scope of the appended claims.

What is claimed is:

1. In a photographic record system, a photographic film having a sound record thereon, said record comprising portions printed in difierent colors, one of said colors being printed on that portion of the record where a selection is recorded and the other color being printed on that portion where silence is recorded, a separate pick-up cell for each color printed on said record, a color filter for each cell, an amplifier fed by the cell which receives the color from that part of the record where a selection is recorded, a sound reproducer fed by said amplifier, and a control device fed by the other said cell, which operates to make said amplifier inoperative when that portion of the record upon which the other color is recorded passes in front of said cells.

2. In a system for producing sound from a sound record, a photographic film having a sound record thereon printed in two difierent colors,

a separate pickup cell for each color, an amplifier and sound reproducer fed by one of said cells and a control device fed by the other of said cells, said control device operating to prevent the production of sound when its cell is exposed to its particular color.

3. In combination, a sound reproducing apparatus having a photographic sound record printed in two colors successively arranged, two light sensitive means for selectively picking up the light transmitted by said record, amplifying and sound reproducing means associated with one of said light sensitive means and control means associated with the other of said light sensitive means for controlling the production of sound.

4. In combination, a sound reproducing apparatus having a photographic sound record track printed in two colors successively arranged, two

light sensitive means associated with two color filters for selectively picking up the light transmitted through said record, amplifying and sound reproducing means associated with one of said light sensitive means and control means associated with the other of said light sensitive means for preventing the production of sound when afiected by its respective color.

5. In .a sound record system, a sound record track having two difierent and distinctive characteristics, one characteristic being present where the selection is recorded and the other characteristic being present where silence is recorded, means controlled by the characteristic associated with the selection for causing the selection to be reproduced as sound, and means controlled by the other characteristic for preventing the production of sound.

6. In a sound record system, a photographic sound record comprising a sound track having successive portions of two or more different colors representing different sound characteristics and means responsive tolight received from the respective colors to control the system in accordance with said characteristics.

7. In a photographic sound record system, a

photographic sound record track made up in two 1 or more diflerent colors successively arranged, a separate pick-up device responsive to each color and means to cause said pick-up devices to have different efiects on the operation of said system.

8. In a system for producing sound from a sound record, a photographic film having a sound record thereon printed in two different colors, a

separate pickup cell for each color, an amplifier fed by one of said cells, and means fed by the other said cell for varying the characteristics of said amplifier.

9. In a system for producing sound from a sound record, a photographic film having a sound record thereon printed in two different colors, a separate pickup cell for each color, an amplifier having a grid electrode fed by one of said cells, and means fed by the other said cell for changing the bias on said grid electrode.

10. In a sound record system, a photographic film having a sound record thereon printed in two different colors, a separate pickup cell for each color, a transformer connected to one of said cells, an amplifier connected to said transformer, and means connected to the other said cell'for short-circuiting said transformer.

11. In a sound record system, a photographic film having a sound record thereon printed in two different colors, a separate pickup cell for each color, a push-pull amplifier connected to one of said cells, and means comprising a space discharge device connected to the other said cell to change the characteristics of said push-pull amplifier.

12. In a sound record system, a photographic film having a sound record thereon printed in two different colors, a separate pickup cell for each color, an amplifier connected to one of said cells, a relay connected to the other said cell, and means responsive to the operation of said relay to change the characteristics of said amplifier.

13. The method of recording sound on a photographic film which consists in coloring in a particular color the portion of the film on which sounds are recorded, and coloring in a different color the portion of the film on which silence is recorded.

14. In a photographic film, a sound track thereon, said sound track comp-rising intervals of recorded sound and intervals of recorded silence, said recorded sound intervals being colored in a particular color, and said recorded silence intervals being colored in a different color, said intervals being arranged in succession.

15. In a sound record system, a photographic sound record track made up in two or more different colors successively arranged, reproducing apparatus controlled by light of one of said colors and means controlled by light of the other of said colors for cutting off said reproducing apparatus.

16. In a sound record system, a photographic record track printed in a plurality of colors successively arranged and a plurality of devices controlled by said record, one of said devices being responsive to both color and intensity of light received from said record and another of said devices being responsive only to the color of said light.

17. The method of producing a photographic sound record which comprises making a normal photographic film sound record track and then giving different distinguishing colors. to portions representing the successive intervals of sound and of silence respectively.

18. A photographic sound record having a sound track of different colors serially arranged along the length of the sound track to represent different sound characteristics. 

